The present invention relates generally to gas turbine engines, and, more specifically, to fans therein.
Passenger carrying aircraft are typically powered by turbofan gas turbine engines. A row of large fan blades is supported by a rotor disk inside an annular nacelle. The engine powers the fan for producing thrust for powering the aircraft in flight.
The fan blades first receive ambient air and are subject to foreign object damage, such as that caused by bird ingestion during flight. The fan blades are relatively large and generate substantial centrifugal force as they rotate during operation. Failure of even one fan blade which liberates the blade from its supporting disk ejects that blade radially outwardly from the engine.
Accordingly, the fan casing surrounding the row of fan blades typically includes a blade containment shield which absorbs the energy of the ejected blade, and contains the blade from being otherwise liberated from the engine.
In such a blade-out mode of failure, the blade is ejected practically instantaneously, yet for a brief instant is within the rotary travel direction of the following or trailing blades in the blade row. The ejected blade will then impact the trailing blade causing damage thereto.
Liberation of the ejected blade creates rotor imbalance and corresponding imbalance loads which must be suitably reacted through supporting structure. Additional damage to one or more of the trailing blades can also affect rotor imbalance, and lead to considerable secondary damage.
Accordingly, it is desired to provide a gas turbine engine fan having reduced damage due to a blade-out failure mode.
A fan blade includes an airfoil having a root and an integral platform. The platform includes forward and aft ends and arcuate first and second sides therebetween. The airfoil root is laterally offset closer to the platform first side than the second side. Impact loads with a trailing blade during a blade-out failure are accordingly distributed for reducing peak loading in the trailing blade and damage thereto.